A periscopic view here is meant to describe a view that is spatially displaced in a peripheral direction from a viewer's normal forward line of sight. Alternatively, a periscopic direction is a line of sight that is parallel to a viewer's normal line of sight but that is displaced above, below, to the right or to the left of a viewer's line of sight by a given distance. The forward line of sight is defined by an imaginary line that that extends forward from the center of a person's field of view while the person is looking forward. Herein, the plane of the normal line of sight is meant to be a plane that contains the forward line of sight.
Periscopes have long been used as viewing devices in submarines. The periscope allows a viewer inside a submersed submarine to view a circumference of area above the surface of the water. Periscopes are also used as toys or spying devices to view around corners without a viewer's normal line of sight being around the corner. Several new uses and improvements for periscopes have been reported.
U.S. Pat. No. 4,934,246 to Benson et al. describes a wide angle trapezoidal periscope useful for wide angle viewing in vehicles such as tanks. The periscope allows the driver to view a field of view above the cockpit of the tank while the driver remains low and inside the tank, thereby keeping the driver out of harms way during a military operation. U.S. Pat. No. 3,596,082 to Doret et al. describes a periscope device used to view objects under water from a buoyant vessel such as a boat. Marschner in U.S. Pat. No. 4,981,346 describes a completely collapsible periscope that can be folded into a single flat piece. A toy periscope is described by Dahlgren in U.S. Pat. No. 4,887,893 whereby the periscope housing is made of a single blown molded piece. In U.S. Pat. No. 5,526,177 Fantone describes a hand held periscope for viewing underwater while the viewer is above the water. Periscopes described in prior art can not be conveniently be used by an underwater viewer such as a diver or by a viewer in an environment where the viewer's hand must be available for other activities. Additionally, periscopes described in prior art are not designed for a viewer to see objects in both a periscopic direction and a normal forward direction simultaneously.
Berke in U.S. Pat. No. 5,170,190 describes using a prism device in combination with an underwater mask to increase the upward and downward peripheral view of an underwater swimmer. U.S. Pat. No. 4,704,014 to Carner, Jr. describes an underwater mask with several optical configurations to enhance the peripheral view of a diver underwater and U.S. Pat. No. 4,932,765 further elaborates on optical configurations to enhance a viewer's peripheral vision using a headgear apparatus. This prior art also fails to describe an apparatus for allowing a viewer to see objects in a periscopic direction underwater or for allowing a viewer to see objects in a periscopic a normal forward direction simultaneously.
There is a need for an apparatus that allows a viewer to see objects in a periscopic direction and in a normal forward direction simultaneously. The apparatus needs to be supported by the viewer's head so that the viewer's hands are free for other activities. There is a further need for an apparatus that allows a viewer to see objects in a periscopic direction and a normal forward direction when the viewer is underwater or in other environments where the eyes and face require protection.